#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
	int ret = 0;
	int arr[] = { 1,2,3,0,5,5,3,2,1 };
	int sz = sizeof(arr) / sizeof(arr[0]);
	for (int i = 0;i < sz;i++)
	{
		ret ^= arr[i];
	}
	printf("%d", ret);
	return 0;
}